Electronic circuit structure, power supply apparatus, power supply system, and electronic apparatus

ABSTRACT

This invention prevents a deterioration of efficiency of a power supply apparatus due to a semiconductor power supply voltage drop, prevents an increase in wasted power, and prevents erroneous operations due to feeder wire voltage drop. In the mounting structure of electronic circuits having a plurality of busbars as current paths on a printed circuit board, the plurality of busbars have almost parallel portions spaced a predetermined distance apart; a span of the parallel portions of the plurality of busbars is greater than the predetermined distance; and in the parallel portions of the plurality of busbars, the plurality of busbars are connected by a wiring pattern. In the switching power supply apparatus built on a printed circuit board, with its output voltage of less than 2 V and its output current of more than 100 A, a means is provided for making the power efficiency higher than 70%.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.11/260,210, filed Oct. 28, 2005, which claims the priority benefit ofJapanese Patent Application No. 2004-314996, filed on Oct. 29, 2004, andNo. 2005-013473, filed on Jan. 21, 2005, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an electronic circuit mountingstructure, a power supply apparatus, a power supply system, and anelectronic apparatus.

In the power supply apparatus and system, a power efficiency is a veryimportant performance.

The power efficiency is a ratio of an output power to an input power ofthe power supply apparatus or power supply system, and an electricitythat is not used as an output is lost mainly as heat within the system.Thus, if the power efficiency is low, a large amount of heat is producedin the power supply system, which means a large amount of electricity islost and not used by electronic circuits or load. This in turn requiresa structure or mechanism for cooling the power supply apparatus andsystem, increasing the cost and size. In addition, this coolingstructure such as fan consumes electricity, further deteriorating thepower efficiency of the power supply system including the fan. A highpower efficiency on the other hand reduces the amount of heat generated,cost and size and enhances the performance of the power supply apparatusand system, contributing to energy saving and prevention of globalwarming.

The output voltage of the power supply apparatus and system forsemiconductor circuits is falling year by year, so their powerefficiency is deteriorating. As for semiconductor circuits, amicrofabrication technology to achieve higher performance andintegration lowers their dielectric strength. This necessarily reducesthe power supply voltage of the semiconductor circuits. However, becauseof increased density integration and faster operation speed, the currentconsumption tends to increase. As a result, semiconductor circuits ofthe same kind tend to have an almost constant power consumption, a lowersupply voltage and an increased current consumption. To meet thistendency of the semiconductor circuits, the power supply apparatus andsystem used for the semiconductor circuits have a reduced outputvoltage. In the power supply apparatus in general, if its output voltageis lowered with its output current kept constant, the amount of heatgenerated does not change greatly, so its power efficiency deteriorates.The power supply apparatus and system used for semiconductor circuitsare thus deteriorating in its power efficiency year by year.

Various technological developments have been conducted to improve thepower efficiency of the power supply apparatus and system or prevent itsdeterioration. All these technologies are intended to reduce a powersupply loss or heat.

A technology of a switching power supply has improved the powerefficiency significantly compared with a voltage dropper type powersupply apparatus, a technology prior to the switching power supply. Thetechnology of the switching power supply has been widely known throughmany publications. Most power supplies for semiconductor circuits arethe switching power supply.

Technologies for preventing switching losses in the switching powersupply, such as a zero voltage switching, have been developed. Theswitching losses are produced by charging or discharging ofelectrostatic capacitance of semiconductor circuits. However, storingenergy in a coil and performing a switching in an appropriate orderenables switching elements to be switched in a state where a voltageapplied to the switching elements is zero, thus eliminating theswitching losses. This is the zero voltage switching technique. Also azero current switching technique has been developed.

To reduce losses in a rectification section of a switching power supply,a synchronous rectification circuit technology has been developed. Theswitching power supply is a circuitry that generates an alternatingcurrent and then rectifies it and has often used semiconductor diodes inthe rectification section. Because the semiconductor diodes have aforward voltage drop of 0.5V to 1V regardless of a passing current, aheat generation may pose a problem in a power supply with a largecurrent output. Replacing these rectification devices with field effecttransistors (FETs) and having them perform a rectification operation insynchronism with an ac power is the synchronous rectification circuittechnology. This technology reduces the voltage drop, which occursbetween electrodes of the rectification devices, down to about 0.1V,significantly reducing the amount of heat generated, compared with theconventional diodes. Since the voltage drop is determined by an on-stateresistance of FET, it is proportional to the flowing current. So, whenan output current of the power supply is small, the amount of heatgenerated is small; and when the output current is high, the generatedheat amount is large, a characteristic that is advantageous to the powersupply. As a result, the synchronous rectification circuit technology,when combined with the above zero voltage switching technology, resultsin most of the losses in the switching power supply being composed ofohmic losses caused by resistive components such as on-state resistancesof switching devices, winding resistances of transformers and wiringresistances, except for small operation power in control circuits.

Efforts to reduce resistive components include a technique that usesthick wiring members such as a metal plate. As disclosed in JP-A2002-345245, this technology uses a metal plate or busbar in a largecurrent wiring path or main current path. The switching power supply isan electronic circuit and thus often employs a construction in whichcomponents are mounted on a printed circuit board for connection. Sincethe wiring portion forming the printed circuit board is normally made ofa thin copper foil, it has a large electric resistance and generates alarge amount of heat when a large current is applied. This technology isintended to reduce the electric resistance and therefore the heatgenerated, by using a metal plate or busbar, a thick wiring member, inthe main current path that carries a large electric current, therebyimproving the power efficiency of the power supply system. According tothe conventional technology disclosed in JP-A 2002-345245, a transformerand an upper part of components are connected through a thick metalplate to reduce electric resistance and realize an improved powerefficiency.

The conventional technology will be explained by referring to FIG. 3. Ona printed circuit board 18 are mounted a transformer 11 andsemiconductor devices 15. Winding leads 12 of the transformer 11 areconnected to metal electrode members 13, which in turn are connected toterminals 14 of the semiconductor devices 15. Other terminals of thesemiconductor devices 15 are connected to a wiring pattern 16 which isconnected to an output terminal 17. That is, the interconnects betweenthe transformer 11 and the semiconductor devices 15 are realized by themetal electrode members 13, and the interconnects between thesemiconductor devices 15 and the output terminal 17 are realized by thewiring pattern 16.

In this example, a printed circuit board with a copper wiring pattern 16measuring 35 μm thick by 10 mm wide by 50 mm long normally has a wiringresistance of about 2.5 mΩ. If the metal plate electrode members 13 are1 mm thick, 10 mm wide and 50 mm long, its resistance is about 0.1 mΩ.Thus, a total wiring resistance is about 2.6 mΩ. Let us consider a casewhere all wires are wiring patterns on the printed circuit board. Inthis case, since the wires connecting the transformer 11 and thesemiconductor devices 15 are also a wiring pattern on the printedcircuit board, there are two wiring patterns with a resistance of about2.5 mΩ and the total resistance is about 5 mΩ. The conventionaltechnology therefore replaces one of the wiring patterns with a metalplate electrode member to reduce the total resistance to 2.6 mΩ, aboutone-half the resistance of the ordinary construction. If the samecurrent flows, the amount of heat produced is proportional to aresistance. When a current of 50 A flows, the wiring with 5 mΩ producesa heat of about 12 W while the wiring with 2.6 mΩ produces heat of about6.5 W, which is about a half of the former.

As described above, this conventional technology has an effect ofhalving the electric resistance and the amount of heat generated in thewiring.

Since this construction has outside the printed circuit board 18, ratherthan on the board, the connections between the terminals 14 of thesemiconductor devices 15 and the metal plate electrode members 13, thesemembers cannot be assembled during the ordinary manufacturing process ofprinted circuit boards. However, the use of manual soldering allows fora technically easy assembling, though it is costlier than an automaticassembling.

As described above, research and development efforts have been made toimprove the power efficiency of power supply apparatus systems.

SUMMARY OF THE INVENTION

In a power supply system and electronic circuits, particularly thosewhich produces a large current output at low voltage, there are caseswhere a power efficiency needs to be enhanced. That is, a large outputcurrent produces a large amount of heat. A lower output voltage resultsin a smaller output power for the same current and the amount of powerlost in the form of heat relatively increases, reducing the powerefficiency. To prevent this situation, there are cases where the powerefficiency needs to be increased. This demand is growing remarkably inrecent years as the operation voltage for semiconductors is decreasing.

With the development of the conventional technology, most of the lossesin the power supply apparatus or the power supply system is caused byresistive components. The resistive components include an on-stateresistance of switching devices, a winding resistance of a transformerand a wiring resistance. There are occasions where resistive componentssuch as wiring resistance need to be reduced.

Particularly in recent years, performances of electronic componentsmaking up the power supply apparatus improve year by year, reducing theresistive components, with the result that the share of wiringresistance increases to about ⅓ the resistive component in some cases.Thus, the reduction in wiring resistance has become important.

Further, since the operation voltage of semiconductor devices isdecreasing, allowable variations and errors of the power supply voltageis also decreasing. A demand for reducing a voltage drop caused by acurrent flowing through wires is also growing notably.

Further, there are cases where it is desired that an assembly be done inthe ordinary printed circuit board manufacturing process for costreduction while at the same time realizing a mounting structure with asmall wiring resistance. That is, a structure may in some cases berequired which allows for an automatic assembly without using a manualwork.

According to one aspect, the present invention provides a mountingstructure of electronic circuits having a plurality of busbars ascurrent paths on a printed circuit board, wherein the plurality ofbusbars have almost parallel portions spaced a predetermined distanceapart; wherein a span of the parallel portions of the plurality ofbusbars is greater than the predetermined distance; wherein in theparallel portions of the plurality of busbars, the plurality of busbarsare connected by a wiring pattern.

According to another aspect, the present invention provides a switchingpower supply apparatus built on a printed circuit board, wherein itsoutput voltage is less than 2 V and its output current is more than 100A, the switching power supply apparatus having a means to make a powerefficiency higher than 70%.

This invention has an effect of reducing the total resistance of wiringportion and also the amount of heat generated in an electronic circuitmounting structure, a power supply apparatus, an electronic circuitboard or in a power supply system. Further, in the power supplyapparatus or the power supply system, this invention has an effect ofimproving the power efficiency to 70% or higher. In the power supplysystem, this invention can reduce a cooling fan in size and weight oreliminate it, contributing to a reduction in the noise of fan and cost.Furthermore, in an electronic apparatus this invention has an effect ofreducing power consumption.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first embodiment.

FIG. 2 is a perspective view of a second embodiment.

FIG. 3 is a perspective view showing a conventional technology.

FIG. 4 is a conceptual diagram of this invention.

FIG. 5 is a conceptual diagram of this invention.

FIG. 6 is a schematic diagram showing a fourth embodiment.

FIG. 7 is a schematic diagram showing a fifth embodiment.

FIG. 8 is a schematic diagram showing a sixth embodiment.

FIG. 9 is an example of the mounting structure of FIG. 4.

FIG. 10 is another example of the mounting structure of FIG. 4.

FIG. 11 is a graph showing the amount of heat produced.

FIG. 12 is a graph showing power efficiencies.

FIG. 13 is a graph showing power efficiencies for different outputvoltages.

FIG. 14 is a graph showing power efficiencies for different numbers ofparallel connections of semiconductor devices.

FIG. 15 is an example circuitry of a switching power supply that appliesthe present invention.

DESCRIPTION OF THE EMBODIMENTS

Now, embodiments of this invention will be described in detail.

1. Embodiment 1

FIG. 1 shows a mounting structure of an electronic circuit in a firstembodiment of this invention and more specifically a mounting structureof a power supply circuit.

On a printed circuit board 36 are mounted a transformer 21, busbars 26,27, 33 and semiconductor devices 31, 32. A winding lead 22 of thetransformer 21 is shaped like pin terminals and connected to a busbar 26via a through-hole 23, a wiring pattern 24 and a plurality ofthrough-holes 25. The busbar 26 is shaped like pin terminals andconnected to a busbar 33 via a through-hole 28, a wiring pattern 29, athrough-hole 30, semiconductor devices 31 and wiring patterns (notshown) in an inner layer of the printed circuit board. The busbar 33 isconnected through a wiring pattern 34 to an output terminal 35.

The similar construction is provided in a path from the transformer 21to a busbar 27, semiconductor devices 32 and the busbar 33.

The busbars are metal plates independent of the structure of the printedcircuit board and intended for carrying electric current.

In this construction, the busbars 26, 27, 33 are 2 mm thick, 10 mm wideand 100 mm long and were found to have a resistance of about 0.1 mΩ. Thebusbar 26 and the busbar 33 are arranged parallel to each other andspaced by a distance L of 10 mm. Their parallel overlapping portion Wmeasures 50 mm. The wiring pattern between the busbar 26 and the busbar33 has a plan view dimension of width W and length L, i.e., 35 μm thick,50 mm wide and 10 mm long. As for the resistance, although a calculatedresistance is 0.1 mΩ, its actual resistance was 0.2 mΩbecause the wiringpattern is connected to the semiconductor devices 31 and complicated inshape. Therefore, the total resistance of the wiring formed between thebusbar 26 and the busbar 33 was about 0.4 mΩ.

The winding leads 22 of the transformer 21 are shaped like a plate andconnected to the printed circuit board via a plurality of through-holesand terminals. That is, they have a busbar structure. The winding leads22 and the busbar 26 are arranged parallel to each other and spaced by adistance of 5 mm. Their parallel overlapping portion spans 25 mm. Thewiring pattern between the winding leads 22 and the busbar 26 has a planview dimension of about 5 mm in width and 25 mm in length. Morespecifically, the wiring pattern is 35 μm thick, 25 mm wide and 5 mmlong and was found to have a resistance of about 0.1 mΩ. A totalresistance of the wiring from the winding lead 22 of the transformer 21to the busbar 33 was about 0.5 mΩ.

The wiring portion with a total resistance of 0.4-0.5 mΩ, when applied acurrent of 50 A, produces a heat of 0.75-1 W.

Compared with the total wiring resistance of about 2.6 mΩ in theconventional technology, this embodiment has a reduced total resistanceof about 0.4-0.5 mΩ, one sixth to one fifth of the conventional totalresistance. Similarly, the amount of heat produced is also reduced.

The busbars 26, 27, 33 and the winding leads 22 of the transformer 21have a pin terminal structure and are inserted into through-holes forconnection with the printed circuit board. These connections are similarin shape and method to the ordinary insertion type electroniccomponents, so they can be assembled in the manufacturing process ofordinary printed circuit boards. This means that an automatic assemblycan be used, lowering the manufacturing cost. Since the cost of theautomatic assembly is one tenth that of manual assembly, the assemblycost of the busbars and metal plate electrode members in this embodimentwas able to be reduced to one tenth.

The connection terminal structure can of course be changed from the pintype to any appropriate shape so that it can easily be used for surfacemounting or surface connection, in addition to the through-holeinsertion connection. The connection terminal may also be formed into acontinuous shape longer or wider than the thickness of the busbar ormetal plate, rather than a plurality of pin terminals. This type ofconnection terminal can also minimize the resistance of the connection,thus achieving the initial object of lowering the wiring resistance.

While in this embodiment, the shape of the busbar parallel portion andthe shape of the wiring pattern almost match, the wiring pattern may beformed smaller than the busbar, e.g., the width of the wiring patternmay be set narrower or larger by several times. What is important isthat the portion through which an electric current flows, i.e., thebusbar parallel portion on the wiring pattern, is wide and short withrespect to the direction of current flow. With this requirement met, theinitial object of lowering the wiring resistance and therefore the heatgeneration can be realized.

Although this embodiment has taken up an application to a power supplyapparatus as an example case, this mounting structure can be implementedin any electronic circuit. Since this structure has an effect ofreducing the resistance, it can be suitably applied to those portionscarrying a large current, such as power supply wiring portions, feedingportions, receiving portions and distribution portion in electroniccircuits.

2. Embodiment 2

FIG. 2 illustrates a second embodiment of this invention of anelectronic circuit mounting structure and more specifically a mountingstructure of a power supply circuit.

The second embodiment has a similar structure to the first embodimentbut there are also differences, which are described as follows.

The transformer 51 has one turn of a platelike secondary winding formedintegral with a lead portion. The lead portion has a plurality ofpin-shaped terminals inserted into through-holes 53 and soldered forconnection with a wiring pattern 54 on a printed circuit board 71. Abusbar 56 has a magnetic core 61 mounted thereon which functions as aninductance, forming an inductor for a smoothing filter required in aswitching power supply circuit. Another busbar 57 also has the similarshape.

In this second embodiment, a large current path comprises two groups. Afirst group is made up of a path from the transformer 51 to the busbar56 to an output terminal 66 and a path from the transformer 51 to thebusbar 57 to an output terminal 70; and a second group is made up of apath from the transformer 51 to the busbar 56, semiconductor devices 59,a busbar 64 and to an output terminal 68 and a path from the transformer51 to the busbar 57, semiconductor devices 60, the busbar 64 and to theoutput terminal 68.

In the first group wiring, the winding lead of the transformer 51 isshaped like a plate and connected to the printed circuit board through aplurality of through-holes and terminals. The winding lead is thereforea busbar structure. The winding lead and the busbar 56 are arrangedparallel to each other, set apart by a distance of 5 mm. Their paralleloverlapping portion is 25 mm long. A wiring pattern located between thewinding lead and the busbar 56 has a plan view dimension of about 5 mmin width and 25 mm in length, more specifically 35 μm in thickness, 25mm in width and 5 mm in length. The wiring pattern resistance was about0.1 mΩ. The busbar including the inductor measures 2 mm thick by 10 mmwide by 150 mm long, and its resistance was about 0.15 mΩ. The currentpath including the busbar 57 also has the similar structure. Thus, thetotal resistance of the first group wiring was about 0.25 mΩ.

In the second group wiring, the wiring pattern 54 formed between thewinding lead of the transformer 51 and the busbar 56 was found to have aresistance of about 0.1 mΩ as described above. The busbar itself,excluding the inductor, measures 2 mm thick by 10 mm wide by 100 mm longand has a resistance of about 0.1 mΩ. The busbar 56 and the busbar 64are arranged parallel on a wiring pattern 58 at an interval L of 10 mm.The parallel overlapping portion W spans 50 mm. A wiring patternprovided between the winding lead and the busbar 56 has a plan viewdimension of width W and length L, i.e., 35 μm thick, 50 mm wide and 10mm long. Its shape is complex and thus its resistance was 0.2 mΩ. Thebusbar 64 is 2 mm thick, 10 mm wide and 100 mm long and its resistancewas about 0.1 mΩ. The current path including the busbar 57 also has thesimilar structure. Therefore, the total resistance of the second groupwiring was about 0.5 mΩ.

As described above, in the second embodiment, the total resistance ofthe wiring carrying a large current was in a range from 0.25 mΩ to 0.5mΩ. In the conventional technology the total wiring resistance was about2.6 mΩ, so this embodiment has reduced the total resistance down to 1/10to ⅕.

In the mounting structure of the power supply circuit, the reason thatthe wiring resistance was able to be reduced is that the wiring employsa busbar with a thickness of 2 mm, substantially thicker than the wiringcopper foil of the printed circuit board, and that the wiring patternsin the printed circuit board connecting a plurality of busbars areshaped so that its width is larger than the length. This is conceptuallyillustrated in FIG. 4 and FIG. 5.

In FIG. 4 and FIG. 5, busbars 80 and 81 are arranged parallel to eachother and their parallel overlapping portions are spaced by a distance Land span a width W. They are connected through a wiring pattern 82 onthe printed circuit board. The wiring pattern 82 also has a width W anda length L. Arrows represent a flow of current. The busbars are formedof a relatively thick metal plate to reduce their resistance. The wiringpattern 82, because it is on the printed circuit board, is formed of athin copper foil. But its resistance can be lowered by increasing itswidth and shortening its length. By setting the busbar and the wiringpattern so that their current directions are almost perpendicular, theycan be connected.

As described above, a fundamental concept or feature of the presentinvention is that the wiring pattern connecting a plurality of busbarsis constructed to have a width greater than its length.

What is described above is only a basic concept and therefore the wiringpattern may be formed into trapezoidal or other shapes, instead of arectangular shape. The busbars need not be strictly parallel to eachother or straight. The only requirement is that the wiring pattern havea greater width than its length with respect to the direction of currentflow.

Further, as described in the first and second embodiment, this wiringpattern may be used for the connection of semiconductor devices andtherefore may be divided. That is, the busbars almost parallel to eachother are so arranged that the span of the parallel overlapping portionsof the busbars is greater than their interval. As long as the paralleloverlapping portions of the busbars are connected to each other throughthis wiring pattern, the object of this invention is achieved regardlessof the detailed shape of the wiring pattern or whether the wiringpattern is divided or not.

FIG. 9 and FIG. 10 show example mounting structures. In these figures,the busbar 80 and the busbar 81 are arranged parallel to each other andtheir parallel overlapping portions have a greater span than theirinterval. Between the parallel overlapping portions there are wiringpatterns 83 and 84 on the printed circuit board which are connected tothe busbars. The wiring patterns 83, 84 are connected with semiconductordevices 86.

The semiconductor devices 86 of FIG. 9 are a three-terminal device withtwo diodes built into it. An anode terminal of the diode is connected toan electrode A on the wiring pattern 83 and a cathode terminal of thediode is connected to an electrode K on the wiring pattern 83. In thiscircuit as a whole, a current flows from the busbar 80 into the wiringpattern 83, from which it passes through the semiconductor devices 86 tothe wiring pattern 84 and to the busbar 81. The wiring patterns 83, 84are spaced from each other by a distance smaller than their sizes. Thesemiconductor devices 86 are connected to the wiring patterns 83 and 84.If a plurality of semiconductor devices are to be connected in parallel,they need only be arranged in the width direction of the wiring patterns83, 84 to increase their parallel number without disturbing the currentpath.

The semiconductor devices 86 shown in FIG. 10 are FETs (Field EffectTransistors), with their drain connected to an electrode D, source to anelectrode S and gate to an electrode G. When applied a signal at theirgate the FETs are switched. Since the signal to the gate is a smallcurrent, the feature size of the wiring pattern 85 is narrow. A largecurrent flows from the busbar 80 to the wiring pattern 83, thesemiconductor devices 86, the wiring pattern 84 and to the busbar 81.This current flow is similar to that of FIG. 9.

3. Embodiment 3

A third embodiment of this invention, though not shown, is a powersupply printed circuit board made up of busbars, wiring patterns andelectronic components. A wiring portion for supplying current toelectronic components comprises busbars and wiring patterns, which issimilar in construction to the first or second embodiment.

Since the wiring portion for supplying electricity has the similarconstruction to the first or second embodiment, the total resistance ofwiring is reduced from the conventional 2.6 mΩ to 0.4 mΩ, which is 1/6.5the conventional resistance. As a result, the amount of heat produced isalso reduced to 1/6.5.

A voltage drop occurs when a current flows through a resistive wiring.When a current 50 A flows, the conventional wiring of 2.6 mΩ produced avoltage drop of 130 mV, whereas the wiring of this invention with aresistance of 0.4 mΩ has reduced the voltage drop to 1/6.5. In thisembodiment, the wiring portion for current supply is used to supply apower of 3.3 V to the semiconductor devices. With the conventionalstructure, there are locations where a 3.9% or 130 mV voltage dropoccurs, sometimes resulting in erroneous operations. With thisinvention, the magnitude of voltage drop is reduced to 40 mV at maximumor 1.2%, with the result that the erroneous operations are eliminated.As described above, this invention has contributed to the realization ofstable operation of electronic circuits and to the improvement ofreliability of electronic devices.

Even a power supply circuit printed circuit board intended solely forelectric connections between printed circuit boards and having noelectronic components mounted thereon, such as a backboard, can employthe technology of this invention to reduce the wiring resistance, themount of heat generated and the voltage drop.

Further, this mounting structure can also be applied to componentproducts or half-completed products of power supply apparatus, to powersupply apparatus without a case or to a power supply module and realizethe similar effects.

4. Embodiment 4

FIG. 6 shows a power supply apparatus, a fourth embodiment of thisinvention.

In FIG. 6, a power supply apparatus 90 has a power circuit 91, a controlcircuit 92 and an interface circuit 93. The power circuit 91 has amounting structure of the third embodiment of this invention. Itreceives a do power from an input terminal 96 and produces an output atan output terminal 94. The control circuit 92 is connected to the outputterminal 94 and monitors a voltage at this point to control the powercircuit 91. The interface circuit 93 is connected to the control circuit92 and performs an on/off control on the power supply apparatus and anormal/abnormal state report, as required, through a terminal 95.

FIG. 15 shows an example power supply circuit diagram of a power supplyapparatus comprising the power circuit 91 and the control circuit 92.

An inverter (MOSFET A-D) converts a dc voltage into an ac voltage byhigh-frequency switching and then the ac voltage undergoes insulationand voltage transformation by a transformer. The ac voltage is rectifiedby a rectification MOSFET (A-B′), smoothed by DCL (smoothing coil L1,L2) and capacitor, and output as a dc voltage. At this time, the outputvoltage is compared with a reference voltage by a voltage comparator,and a PWM control circuit controls the inverter and the rectificationMOFET to make the output voltage a desired value.

This power supply apparatus uses the mounting structure of the firstembodiment in the power circuit, so the total resistance of wiringportion is reduced to ⅙ to ⅕ that of the conventional technology. Theamount of heat generated in the wiring portion also has decreased to ⅙to ⅕. Therefore, the total amount of heat generated in this power supplyapparatus is reduced in half and its power efficiency improved to morethan 70%. The power efficiency is a ratio of the output power to theinput power of the power supply apparatus 90.

Next, the amount of heat generated and the power efficiency of the powersupply apparatus according to this invention will be described in detailby referring to FIG. 11 to FIG. 14.

FIG. 11 is a graph showing the amount of heat generated, with anabscissa representing an output current of the power supply and anordinate representing the amount of heat generated. Two curves shown area characteristic curve, marked , of the power supply according to thisinvention and a characteristic curve, marked ▴, of the conventionalpower supply. The output voltages of both power supplies are 1.2 V. Inthe entire range of the graph, the amount of heat generated by the powersupply of this invention is less than one-half that of the conventionalpower supply. The power supply of this invention produces a small amountof heat.

FIG. 12 is a graph showing a power efficiency, with an abscissarepresenting an output current of the power supply and an ordinaterepresenting a power efficiency. That is, this graph shows a ratio of anoutput voltage to an input voltage. The power efficiency of the powersupply according to this invention is 80% to 90% in an output currentrange of between 10 A to 100 A. The conventional power supply has apower efficiency of 50% to 70% in the same current range. The powersupply of this invention is higher in power efficiency than theconventional power supply.

In FIG. 12 the efficiency is high in the output current range of about20 A to 60 A, but begins to deteriorate at a higher output current anddroops at around 100 A. For a large current higher than about 100 A thepower efficiency falls, so this invention contributes to improving thepower efficiency. This tendency is significant, particularly with aninsulating type power supply, i.e., one in which the power supply inputside and the output side are isolated by a transformer.

FIG. 13 is a graph showing a power efficiency when the output voltage ofa power supply of this invention is changed. Three characteristic curvesshown are, from top to bottom, for an output voltage of 2 V, 1.2 V and1.0 V. As the output voltage decreases, the efficiency deteriorates.This is a general, universally observed characteristic for any powersupply. The technology of this invention has a remarkable efficiencyimprovement effect for an output voltage of 2 V or lower. This isexplained as follows. As can be seen from this graph, for the outputvoltage higher than about 2 V, the power efficiency is high and thereare no large power efficiency differences. Therefore, the technology ofthis invention has a significant power efficiency improvement effect forthe output voltage of 2 V or lower.

FIG. 14 is a graph showing a power efficiency when the parallelconnection number of the semiconductors is changed. Characteristiccurves represent, from top to bottom, a case where the semiconductorparallel number is increased by about three times (marked Δ), a case forthe second embodiment (marked ◯) and a case where the semiconductorparallel number is reduced almost in half (marked □). In the secondembodiment, the power efficiency is 80% to 90% in the output currentrange of between 20 A and 100 A. When the semiconductor parallel numberis increased by about three times to halve the total resistancecomponent R, the power efficiency is 88% to 93% in the same currentrange. When the semiconductor parallel number is reduced almost in half,the power efficiency is 70% to 83% in the same current range. Thesemiconductor parallel number may be changed by a method that changesthe span of the parallel overlapping portion of the busbars and by amethod that increases or decreases the number of busbars. Depending onthe size, shape and cost and according to a target output current, thepower efficiency can be set arbitrarily in a range from about 70% tomore than 90% or theoretically close to 100%. It is due to the effect ofthe technology of this invention that the design of a power supply withsuch a high power efficiency becomes possible.

The assembly process has conventionally required a manual work but thispower supply apparatus allows for a fully automatic assembly process. Asa result, the assembly time could be halved and the assembly costreduced by 30%.

The use of the mounting structure of the second embodiment in the powercircuit can produce the similar effect.

While the conventional structure uses a printed circuit board with 14layers to make a copper pattern thick to reduce the resistance of wiringpattern as much as possible, the technology of this invention allows theprinted circuit board to have only six layers. The reduced number oflayers in the printed circuit board has resulted in the cost of printedcircuit boards being reduced in half and the cost of power supplyapparatus being reduced by 10%.

There are various types of power supply apparatus, including one with orwithout a control circuit, one with a complex control circuit, one withor without a cooling mechanism, one with a rectification circuit, onewith an ac/dc converter, and one with a harmonic wave suppressionfunction. In whatever type of the power supply apparatus, the sameeffect as described above can be obtained.

5. Embodiment 5

FIG. 7 shows a power supply system as a fifth embodiment of thisinvention.

In FIG. 7, a power supply system 100 has power supply apparatus 101 and102 and a control circuit 103. At least one of the power supplyapparatus 101, 102 is the power supply apparatus of the fourthembodiment of this invention, and the control circuit 103 performs anon/off control and monitoring on the power supply.

Since the power supply system uses the power supply apparatus of thisinvention, the total resistance of the wiring portion is 1/10 to ⅕ thatof the conventional technology and the amount of heat produced in thewiring portion is also 1/10 to ⅕ that of the conventional technology.Therefore, the total amount of heat produced in the power supply systemis reduced to one-half and the power efficiency is improved to more than70%. As a result, the cooling requirement can be met by a naturalconvection, making it possible to eliminate a cooling fan that has beenrequired in the conventional technology. This in turn has resulted inreductions in size and cost.

Further, while the assembly process has conventionally required a manualwork, the power system of this invention can be assembled fullyautomatically. As a result, the assembly time decreases to one half andthe assembly cost is reduced by 30%.

Generally, there are various types of power supply system, including onewith a plurality of power supply apparatus as in this embodiment, onewith many power supply apparatus or with a single apparatus, one with orwithout a control circuit, one with a complex control circuit, and onewith or without a cooling mechanism. In whatever type of power supplysystem, the same effect as described above can be produced.

6. Embodiment 6

FIG. 8 shows an electronic apparatus as a sixth embodiment of thisinvention.

In FIG. 8, an electronic apparatus 110 comprises a power supply system112 and an electronic circuit 111. The power supply system 112 is thepower supply system of the fifth embodiment of this invention andsupplies electricity to the electronic circuit 111. The electroniccircuit 111 partly uses the electronic circuit board of the thirdembodiment of this invention.

Since this electronic apparatus uses the power supply system of thisinvention, the power consumption of this electronic apparatus was ableto be reduced by 15%. This in turn reduces the burden on a powerreceiving facility that supplies electricity to the electronicapparatus, and also reduces the size of the facility This will also leadto an elimination of a cooling facility for the electronic apparatus.Further, because of the small power consumption, the electronicapparatus of this invention can contribute to saving energy and oil andother resources. It can also make contributions to reducing emissions ofglobal warming gases, such as carbon dioxides.

Further, since the power supply system of the electronic apparatus canbe automatically assembled, the cost of assembling the electronicapparatus can also be reduced.

Further, in electronic apparatus for general users, many commercialpower supply cables have a limitation of 15 A. An improved powerefficiency of the power supply system allows 15% more electroniccircuits to be mounted for the same power supply cable, improving theperformance of the electronic apparatus.

Further, since the electronic circuit board of the third embodiment ofthis invention is used in the electronic circuit 111, the operationstability of the electronic circuit is improved, enhancing thereliability of the circuit operation by 10 times.

Although the above description has been made of example embodiments, itis apparent to those skilled in the art that the present invention isnot limited to these embodiments and that various changes andmodifications may be made without departing from the spirit of theinvention or from the scope of the appended claims.

1. A power supply device comprising: a mounting structure for electroniccircuits having a plurality of busbars as current paths on a printedcircuit board; a power circuit; and a control circuit for controllingthe power circuit, wherein the plurality of busbars have almost parallelportions spaced a predetermined distance apart, wherein a span of theparallel portions of the plurality of busbars is greater than thepredetermined distance, wherein in the parallel portions of theplurality of busbars, the plurality of busbars are connected by a widewiring pattern whose width is larger than its length with respect to adirection along which a current flows, and wherein a wide wiring patternwhich connects a pair of adjacently located first and second busbars isarranged in such a manner that its width is larger than its length withrespect to a direction along which a current flows from the first busbarto the second busbar.
 2. A power supply system comprising: a mountingstructure for electronic circuits having a plurality of busbars ascurrent paths on a printed circuit board; and a power source forsupplying power to the electronic circuits, wherein the plurality ofbusbars have almost parallel portions spaced a predetermined distanceapart, wherein a span of the parallel portions of the plurality ofbusbars is greater than the predetermined distance, wherein in theparallel portions of the plurality of busbars, the plurality of busbarsare connected by a wide wiring pattern whose width is larger than itslength with respect to a direction along which a current flows, andwherein a wide wiring pattern which connects a pair of adjacentlylocated first and second busbars is arranged in such a manner that itswidth is larger than its length with respect to a direction along whicha current flows from the first busbar to the second busbar.
 3. A powersupply system comprising: a mounting structure for electronic circuitshaving a plurality of busbars as current paths on a printed circuitboard; a power source device including a power circuit and a controlcircuit for controlling the power circuit; and a power source forsupplying power to the power source device, wherein the plurality ofbusbars have almost parallel portions spaced a predetermined distanceapart, wherein a span of the parallel portions of the plurality ofbusbars is greater than the predetermined distance, wherein in theparallel portions of the plurality of busbars, the plurality of busbarsare connected by a wide wiring pattern whose width is larger than itslength with respect to a direction along which a current flows, andwherein a wide wiring pattern which connects a pair of adjacentlylocated first and second busbars is arranged in such a manner that it'swidth is larger than its length with respect to a direction along whicha current flows from the first busbar to the second busbar.
 4. Anelectric device comprising: a mounting structure for electronic circuitshaving a plurality of busbars as current paths on a printed circuitboard; and a power source for supplying power to the electroniccircuits, wherein the plurality of busbars have almost parallel portionsspaced a predetermined distance apart, wherein a span of the parallelportions of the plurality of busbars is greater than the predetermineddistance, wherein in the parallel portions of the plurality of busbars,the plurality of busbars are connected by a wide wiring pattern whosewidth is larger than its length with respect to a direction along whicha current flows, and wherein a wide wiring pattern which connects a pairof adjacently located first and second busbars is arranged in such amanner that its width is larger than its length with respect to adirection along which a current flows from the first busbar to thesecond busbar.
 5. An electric device comprising: a mounting structurefor electronic circuits having a plurality of busbars as current pathson a printed circuit board; a power source device including a powercircuit and a control circuit for controlling the power circuit; and apower source for supplying power to the power source device, wherein theplurality of busbars have almost parallel portions spaced apredetermined distance apart, wherein a span of the parallel portions ofthe plurality of busbars is greater than the predetermined distance,wherein in the parallel portions of the plurality of busbars, theplurality of busbars are connected by a wide wiring pattern whose widthis larger than its length with respect to a direction along which acurrent flows, and wherein a wide wiring pattern which connects a pairof adjacently located first and second busbars is arranged in such amanner that its width is larger than it length with respect to adirection along which a current flows from the first busbar to thesecond busbar.